1. Field of the Invention
The present invention relates to an optical network system, particularly to an integrated passive optical network (PON) system.
2. Description of the Related Art
For transmitting and receiving a large volume of data through a communication network, the communication network has to speed up and broaden in an access network for connecting a subscriber to the communication network, and the introduction of a passive optical network (PON) is performed. The PON is a system where an optical line terminator (OLT) connected to an upper communication network and optical network units (ONUs) including terminals (PC or phone) of plural subscribers are connected to each other through an optical distribution network (ODN) including a trunk optical fiber, an optical splitter and plural branch optical fibers. The main technology used nowadays is a time-division multiplexing (TDM)-PON.
However, many researchers have reported wavelength-division multiplexing (WDM) access systems designed to cope with the increasing capacity of optical access networks. The WDM-PON increases the transmission capacity more than the TDM-PON. Since WDM access systems can share a fiber and assign an individual wavelength path to each user, the transmission capacity can be increased easily and changed independently. However, the TDM-PON is directly dismantled and replaced with the WDM PON, which is uneconomical. Besides, ONUs have to have different and precisely wavelength-tuned light sources in the system. Consequently, ONUs become too expensive. If the service provider provides an optical signal to a user, Rayleigh backscattering will occur. When the wavelengths of an upstream signal and the Rayleigh backscattering overlap, an efficiency of the upstream signal becomes bad.
In view of the problems and shortcomings of the prior art, the present invention provides an integrated passive optical network system, so as to solve the afore-mentioned problems of the prior art.